DE112013001790T5 - Vibration control in data storage units - Google Patents

Abstract

Data storage units (1) are provided in which a track guidance system is able to counteract the effects of vibrations. A storage unit comprises a housing (2) of the unit and a read / write head (6) for reading and writing data on a data track (10) of a storage medium (5) which, in use, is carried by the housing of the unit. An actuator system (7) is mounted on the housing (2) of the unit to cause movement of the read / write head (6) relative to the data track (10) to align the head with the data track. The actuator system (7) has a plurality of degrees of freedom to effect movement, and a control unit (12) controls the actuator system (7) to effect movement. At least one housing vibration sensor (8) is provided on the housing (2) of the unit in order to generate a signal which indicates vibrations of the housing. At least one actuator system vibration sensor (9) is provided on the actuator system (7) to generate a signal indicative of vibrations of the actuator system. The control unit (12) is able to process the signals from the housing and actuator vibration sensors (8, 9) in order to derive at least one coupling signal which indicates a vibrational coupling between the degrees of freedom and to the actuator system (7) as a function of the at least one coupling signal and the signal from the at least one housing vibration sensor (8).

Description

This invention relates generally to vibration control in data storage units, and more particularly to tracking under vibration conditions in such units. Provided are data storage units in which tracking is capable of counteracting the effects of vibration.

In data storage devices such as tape drives and disk drives, an actuator system effects movement of the read / write head relative to a data track of the storage medium to align the head to the data track. A servo control system utilizes servo data read from the storage medium to control the actuator system to maintain head / track alignment during operation. In tape drives, for example, the servo control system corrects the lateral position of the head relative to the longitudinal tracks on the tape, as well as rotational positioning, to counteract skew between head and tape. Reliable operation of such storage units requires stable operation of the servo control system under vibration conditions. Typically, standard vibration profiles are used to describe the vibration specifications for the occurrence of accelerations under which the memory unit must continue to function reliably. The demand for higher storage densities makes it increasingly difficult to meet the functional specifications under vibration conditions. For example, in tape drives, the increasing density of the tape tracks further narrows the allowable tracking error tolerance during read / write operations, so that an improved tracking function is needed to provide the additional tracking margin that is at least required for reliable tape operation under vibration conditions.

Currently, there are two main techniques for improving the tracking function in vibration environments. A first technique used with tape drives involves switching between two tracking controllers. A high bandwidth controller has better performance during vibration, but is less reliable during normal operation. Therefore, upon detection of vibration, the tape drive switches from a low bandwidth controller to a higher bandwidth controller. The main drawbacks of this concept are that it relies on detecting the onset of vibration and that there is transient behavior during switching between the two control units. Due to the mixed control concept, it is also difficult to evaluate stability and functional strength.

A second technique for dealing with vibration conditions uses accelerometers to measure the applied vibrations. Some implementations of this technique use an accelerometer attached to the actuator on the head, for example in the disk drives incorporated in the U.S. Pat. No. 6,407,876 and 5,426,545 are described. Other implementations of this technique use accelerometers mounted on the housing rather than on the actuator of the drive. Examples are in the U.S. Patent No. 7,468,857 and in "Increased disturbance rejection in magnetic disk drives by acceleration feedforward control and parameter adaptation", White and Tomizuka, Control Eng. Practice, Vol. 5, No. 6, pp. 741-751, 1997. Here, the data of the accelerometer is used in a control unit with feedforward control to correct the position of the actuator.

According to an embodiment of an aspect of the invention, there is provided a data storage unit comprising:
a housing of the unit;
a read / write head for reading and writing data on a data track of a storage medium that in use is carried by the housing of the device;
an actuator system mounted to the housing of the unit for effecting movement of the read / write head relative to the data track to align the head with the data track, the actuator system having a plurality of degrees of freedom for effecting movement;
a control unit for controlling the actuator system to effect the movement;
at least one housing vibration sensor provided on the housing of the unit to generate a signal indicative of vibrations of the housing; and
at least one actuator system vibration sensor provided to the actuator system to generate a signal indicative of vibrations of the actuator system;
wherein the control unit is capable of processing the signals from the housing and the actuator vibration sensor to derive at least one coupling signal indicative of a vibration coupling between the degrees of freedom and the actuator system in response to the at least one coupling signal and the signal to control the at least one housing vibration sensor.

Memory units embodying this invention use sensors, such as accelerometers, both on the housing of the Unit as well as on the actuator system. The signals from these sensors, which indicate vibrations of the housing of the unit or the actuator system, are processed by the control unit to obtain at least one coupling signal indicative of a vibratory coupling between different degrees of freedom of the actuator system. This coupling signal is then used by the controller together with the vibration signal (s) of the housing to control the actuator system to effect head / track alignment. This, as discussed in more detail below, is suitably implemented via a combined feed-forward control concept. In this way, in embodiments of this invention, coupling effects between the various degrees of freedom of the actuator system may be estimated and taken into account by the servo control system. For example, coupling effects between the degree of freedom related to the lateral position and the skew in tape drives can be estimated and appropriately handled by the tracking control unit. As a result, an improved tracking function can be achieved under vibration conditions that allow for more reliable operation at increased storage densities.

The housing of the unit on which the vibration sensor (s) are provided has the major part of the unit relative to which the actuator system effects the head / track alignment movement. Of course, the housing itself may include a number of components, such as a frame and / or enclosing elements, along with various other substantially stationary components relative to which the head and / or storage medium are moved to control alignment.

The various degrees of freedom of movement of the actuator system generally depend on the particular type and configuration of the storage unit, the storage medium, the head, and the actuator system. The particular number and arrangement of vibration sensors used in a particular system also depends on the design of the system. In a tape drive having translational and rotational degrees of freedom for the head / tape alignment movement, a single sensor on the housing and actuator system may be sufficient, as will be explained below. However, additional sensors could be used in systems with only two degrees of freedom, for example, for the purpose of improved accuracy / averaging or detecting different motions in different dimensions. Systems with more than two degrees of freedom and additional coupling effects may use additional sensors to accommodate these additional parameters. The particular manner in which the sensor signals from the housing and actuator are processed to derive the desired coupling signal (s) may accordingly be different. However, the basic functional principles of units embodying the invention will be apparent from the description herein, and suitable implementations for a particular system will be readily apparent to those skilled in the art.

The actuator system may generally include one or more actuator mechanisms that make up this system, for example, for moving the head and / or storage medium with different degrees of accuracy in a particular degree of freedom for the alignment process. For example, coarse and fine actuator mechanisms may be provided for a given dimension. In principle, the actuator system could move the head and / or storage medium to effect head / track alignment. Usually, however, the read / write head is mounted on the actuator system, and the relative movement for the head / track alignment is performed at least in part by the movement of the head. In this case, for a good estimate of the coupling between different degrees of freedom, the unit preferably includes a first actuator vibration sensor arranged to detect the vibrations of the actuator system being transmitted to the head. This sensor thus provides a good level of vibration experienced by the head. The unit preferably also includes a first housing vibration sensor located on the housing in the region of the head to detect the vibrations of the housing which are transmitted to the head. This sensor thus provides a good measure of the applied vibrations. As indicated above, additional sensors may optionally be provided depending on the configuration of the unit.

The control unit may be capable of deriving a coupling signal in response to the difference between the signal from the actuator vibration sensor and the signal from the housing vibration sensor. Such a coupling signal may depend directly or indirectly on this difference, for example via direct subtraction of signals or after processing the signals in some way. In preferred embodiments, the control unit includes feedforward logic for generating a control signal for controlling the actuator system, the control logic being capable of providing a first correction to the control signal in response to the signal from a housing vibration sensor and a second Apply correction of the control signal depending on a coupling signal.

Preferred embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

1 is a schematic representation of a tape drive embodying the invention;

2 the two degrees of freedom of movement for the head / tape alignment in the tape drive of 1 shows;

3 Fig. 12 is a schematic illustration of a servo control system in the tape drive;

4 illustrates the coupling between the two degrees of freedom in the tracking control system;

5 represents the frequency responses of the actuator mechanisms for each degree of freedom;

6a and 6b Show results of measurements on the drive under vibration conditions;

7 a schematic representation of a transverse position control system for the drive of 1 is;

8th Measurements of vibration sensors present in the drive of 1 be used; and

9 Results shows that with the control system of 7 were obtained.

1 Figure 10 is a simplified schematic illustration of an exemplary tape drive embodying the invention and illustrates essential elements involved in the function to be described. The drive 1 has a drive cage 2 with a slot 3 for inserting a tape cassette, which is schematically in 4 is indicated. In operation, a magnetic tape and tape guiding system (not shown) carries the magnetic tape 5 from the cassette 4 at a read / write head 6 past to read and write data on the longitudinal data tracks on the tape. The read / write head 6 is on an actuator system 7 attached, which in turn on the housing 2 the unit is attached. In the drive 1 Two vibration sensors are provided for detecting vibrations during operation. A housing vibration sensor in the form of the accelerometer 8th is on the drive cage 2 attached to generate a signal indicating vibrations of the drive housing. An actuator vibration sensor in the form of the accelerometer 9 is on the actuator system 7 mounted to produce a signal indicative of vibrations of the actuator system. Arrangement and function of the accelerometer 8th . 9 will be discussed in more detail below.

The actuator system 7 from drive 1 For example, which may be based on an IBM Linear Tape Open (LTO) tape drive or a proprietary magnetic tape drive, has two degrees of freedom for effecting movement of the head 6 in relation to the band 5 to align the head with a data track. (IBM is a trademark of International Business Machines Corporation). In particular, the actuator system 7 functionally capable of translating the head 6 in a transverse direction relative to the longitudinal data track and also a rotational movement of the head 6 to counteract the skew between the head and the belt. This is shown schematically in 2 that illustrates the head 6 relative to a longitudinal data track 10 on the tape 5 represents. (In practice, the head contains 6 usually multiple read / write elements for simultaneous read / write operations on multiple parallel data tracks on the tape 5 , However, to understand the system to be described, it is sufficient to consider the function with respect to a single track.) The translational motion through the actuator system adjusts the transverse position of the head perpendicular to the data track. The rotational movement adjusts the angle θ between the head alignment and the transverse direction of the belt to eliminate the skew occurring between the head and belt during operation. The slip angle θ is ideally zero during operation. The adjustments of transverse position and rotation (skew) are made by respective actuators of the actuator system 7 to move the head 6 causes. The individual actuator mechanisms correspond to a well-known shape, and many of them have multiple actuators that provide different degrees of motion accuracy. The transverse position actuator, for example, usually has a coarse actuator and a fine actuator for coarse and fine adjustments.

The drive 1 includes a servo control system for controlling the actuator system 7 (hereinafter simply referred to as the "actuator") to provide appropriate movement of the head 6 effect, so that the head / track alignment is maintained. The servo control system is shown schematically in FIG 3 shown. During read / write operations read servo sensors on the head 6 Data stored in rigidly assigned servo tracks on the tape 5 are recorded. The resulting servo read signals are from a servo control unit 12 received, which has a control logic for implementing the lateral position and the skew control functions. The servo control unit 12 in this illustration includes the servo channel for processing the servo read signals to obtain estimates of the current lateral position error and tape-to-head skew angle. The servo control unit then generates control signals u _y and u _s for controlling the actuator 7 to effect appropriate corrections to the lateral position and skew degrees of freedom, respectively.

In an ideal system, the lateral and slip degrees of freedom would be completely independent of each other, which would not affect movement in one dimension by movement in the other. However, the description of the characteristics of an actuator integrated in a drive shows that there is a coupling between the two degrees of freedom. This will be in 4 which is a schematic representation of the mechanical properties of the lateral position control system. Here, K _{y represents} the transfer function of the transversal position (TP) control logic that passes through the block 20 the servo control unit 12 is shown. The TP control unit 20 receives a positional error signal (PES) stored in the servo control unit 12 is calculated from the measured lateral position y _{m of} the head relative to the band, as derived from the servo signals, and the desired or target lateral position y _t . The properties of the actuator 7 , which is the TP actuator 21 and the skew actuator 22 are shown in the figure by the four blocks labeled G _yy , G _ys , G _ss and G _sy . G _yy represents the transfer function of the TP actuator 21 in response to the lateral position control signal u _y from the TP control unit 20 G _ys represents the transfer function of the TP actuator 21 in response to the skew control signal u _s , that from the servo control unit 12 in 3 is produced. The positional outputs of the blocks G _yy and G _ys are summed to produce a lateral position y which is subject to the disturbance d _y caused by the lateral belt movement in operation to indicate the final transverse position of the head relative to the belt. The characteristics of the skew actuator 22 in response to the control signals u _s and u _y are similarly represented by the transfer functions G _ss and G _sy , giving a slip angle θ which is subjected to the disturbance d _θ due to the skew of the _tape to determine the final rotational position of the Head in relation to the band to produce. The shaded blocks G _ys and G _sy in this figure thus represent the coupling effects in the actuator 7 dar. The various transfer functions in 4 can be identified by appropriate measurements within the drive, and the frequency responses obtained for these measurements in an exemplary drive 1 are in 5 shown.

The servo control system in the drive 1 must be designed to remain fully operational during operation, even when vibrations occur, for example due to external vibration or impact or due to the internal operation of parts of the drive itself 1 shown accelerometer 8th . 9 are provided for this purpose and the outputs of these accelerometers are utilized in a particular way by the servo control system for highly efficient vibration suppression. The vibration suppression functionality will be described below with particular reference to the lateral position control in the servo system.

The housing and actuator accelerometer 8th . 9 are arranged on the housing or the actuator so that they are vibrations in the direction of the transverse movement of the head 6 detect. In this particular embodiment, the accelerometers are 8th . 9 nanoscale MEMS (micro-electro-mechanical systems) digital output accelerometers that provide three-dimensional operation that provides sensory axes in three mutually perpendicular directions. The housing accelerometer 8th located on the drive cage 2 in the area of the head 6 , as in 1 indicated so that it detects vibrations of the housing, which are transmitted to the head. The output of the housing accelerometer 8th thus provides a good measure of the applied vibrations that propagate to the drive cage near the head position. The actuator accelerometer 9 is to the actuator 7 placed so that it detects the vibrations of the actuator, which are transmitted to the head. Although this accelerometer is to simplify the illustration in 1 above the actuator 7 however, it is preferably attached to the bottom of the fine actuator mechanism of the transverse position actuator in this example. The output signal of the actuator accelerometer 9 thus provides a good measure of the total vibration acting on the actuator and spreading to the head.

To the vibration effects in the drive 1 to illustrate shows 6a FIG. 5 is a graph of power spectral density (PSD) versus frequency based on accelerometer measurements in an exemplary drive. FIG 1 , The drive was Mounted on a vibrating table that was propelled to the drive 1 to vibrate on which another accelerometer was mounted to measure the applied vibrations. The three curves in 6a are measurements from the vibrating table accelerometer ("vibrating table"), the casing accelerometer 8th ("Drive") and the actuator accelerometer 9 ( "Actuator"). It can be seen that the housing accelerometer 8th good measures the acting vibrations, which are pronounced at frequencies up to about 100 Hz. The actuator accelerometer 9 also measures the additional effects on the actuator caused by the coupling discussed above between the skew and the lateral position degrees of freedom. The effect of this vibration coupling is as in 6b also visualizes in position error signal (PES) spectrum at 100 to 200 Hz.

The servo control unit in the drive 1 processes the signals from the housing and actuator accelerometer 8th . 9 to provide a vibration control that accommodates the coupling effects described above. 7 Figure 3 is a schematic block diagram illustrating the lateral position control system 30 under vibration conditions, showing the shape of the lateral position (TP) control unit incorporated in the servo control unit 12 from 3 is used. The TP control unit commonly used in 31 3, has feedforward logic for implementing a combined concept of feedforward that accommodates the coupling effects. The TP control unit 31 generates a lateral position control signal u _y for controlling a movement of the head in the transverse direction by the actuator 7 , as described above. The TP control unit contains the function block 33 with the transfer function K _y , which converts the basic lateral position control in response to the position error signal PES, as already for 4 described. The control unit 31 contains two more function blocks 34 and 35 with the transfer functions K _FFv or K _FFc . block 34 takes as input the acceleration signal a _D , that of the accelerometer 8th is output, and applies a first correction to the control signal u _y in response to the signal a _D. block 35 takes as input a coupling signal a _C and applies a second correction to the control signal u _y in response to this coupling signal. The coupling signal a _C is from the control unit 31 and indicates the coupling between the skew and the lateral position degrees of freedom. In particular, the control unit receives 31 from the actuator accelerometer 9 both the acceleration signal a _D and the acceleration signal a _A and derives the coupling signal a _C in dependence on the difference between the two acceleration signals. In this simple example, the coupling signal a is _C is generated by a direct subtraction of the housing accelerometer signal a _D by the actuator accelerometer signal _A a. 8th represents the acceleration over the frequency spectrum corresponding to the signals a _A , a _D and a _C based on measurements on an exemplary drive 1 equivalent. The resulting coupling signal a _C provides a good measure of the effect of vibratory coupling on the actuator and head due to skew / cross position coupling. The control unit 31 controls the actuator 7 thus in dependence on the coupling signal a _C and the housing acceleration signal a _D and the position error signal PES.

The properties of the actuator 7 in the TP control system 30 are in 7 through the blocks 37 . 38 and 39 represented by the transfer functions G _yy , G _ya and G _ysa . G _yy represents the basic transfer function of the TP actuator 21 in response to the lateral position control signal u _y represents. G _ya represents the transfer function of the TP-actuator 21 in response to the applied vibrations as measured by the accelerometer signal a _D. This results in adjustment because of the lateral position output y _G of block 37 , G _ysa represents the transfer function of the TP actuator 21 in response to the effect of the vibration coupling represented by the coupling signal a _c . This results in the adjustment d _{c of} the output y _G of block 37 , The resulting position y is subject to another perturbation d _LTM caused by the lateral belt movement to indicate the final transverse position of the head relative to the belt.

The feedforward logic blocks 34 and 35 the control unit 31 are designed to counteract the effects of applied vibration and vibration coupling. For deriving the functions K _FFv and K _FFc , the transfer functions G _yy , G _ya and G _{ysa of} the actuator _blocks 37 . 38 and 39 be used. These transfer functions can be estimated based on measurements within the drive. The blocks 34 and 35 the control unit can be configured then on the basis of the model of transfer functions that are at a required degree of accuracy, for example, K _FFv = -G G _yy ^-1 _ya obtained. In general, the logic function blocks of the control unit could 31 be implemented as software or hardware or as a combination thereof, for example via a combination of software and digital circuits. Suitable reactions will be readily apparent to those skilled in the art. Digital circuits, for example, based on a digital filter circuit of a well-known form, can be readily configured to implement a desired transfer function.

In a basic implementation of the control unit 31 can the feedforward blocks 34 and 35 simply be implemented as a fixed gain amplifier. 9 illustrates results for such a conversion using the transfer functions K _FFv = -1 and K _FFc = +1. The three curves shown in this figure compare the PES spectrum obtained in three different control scenarios. The curve labeled "FF2" indicates the results obtained using the control unit 31 with K _FFv = -1 and K _FFc = +1. The curve marked "FF1" indicates the results that are only available with Block 34 for the forward control in the control unit 31 were received, ie excluding the block 35 converted coupling term (K _FFv = -1 and K _FFc = 0). The curve labeled "without FF" indicates the results without _{feedforward control} (K _FFv = 0 and K _FFc = 0). The standard deviation of the position error signal in each case is as follows: without FF 194 nm with FF1 186 nm with FF2 155 nm.

It can be seen that, even with such a simple implementation of the terms K _FFv and K _FFc, by taking into account the coupling between the skew and the lateral position degrees of freedom, the concept of the combined feedforward control of the control unit 31 provides a significant improvement in the PES function. More complex implementations of control blocks 34 and 35 can be configured as needed to provide a desired level of performance. In general, however, an improved function can be expected in terms of the standard deviation of the PES signal, as well as the reduction of peak PES, which can lead to an abort of read / write operations.

While in operation the emphasis has been placed on the above transverse position control, the combined feedforward control system may also be implemented in the same manner for the skew dimension to take into account the effects of the vibratory coupling on the skew control system. In such an embodiment, for example, a sensor axis of the accelerometer 8th . 9 be used to detect the vibrations in the transverse direction, the two other axes are used to detect rotational movements. Alternatively, additional accelerometers could be used for the rotation measurements. Some examples of other possible alternatives and modifications are given below.

Although a direct subtraction of the accelerometer signals is used to derive the above coupling signal, in general the coupling signal could be derived after processing the housing and actuator signals in any way, for example after weighting by applying certain gains to the signals or after an averaging process, when multiple signals from additional accelerometers are available.

Although MEMS accelerometers are used in the preferred embodiment, other sensors could generally be used to provide signals indicative of the vibrations to be measured. For example, if a voice coil movable in a magnetic field is incorporated in the actuator system, the vibration induced movement of the coil causes back EMF to be induced in the coil, and this could be recognized as a measure of the vibration.

While implementation has been described for a tape drive, the combined feedforward control system can of course be applied to other storage devices, such as disk drives, where similar considerations apply. Systems with more than two degrees of freedom and additional coupling effects may use additional sensors, and additional coupling signals may be derived and used by the control system. In general, the number and positioning of sensors used in a particular system may depend on the particular type and configuration of the memory unit, the storage medium, the head, and the actuator system, and the particular manner in which the housings and actuator sensor signals may be processed to derive the one or more desired coupling signals (e) may be accordingly different. Suitable reactions for a particular system will be apparent to those skilled in the art.

It is understood that many other changes and modifications may be made to the described exemplary embodiments without departing from the scope of the invention.

Claims (14)

A data storage unit comprising: a housing ( 2 ) the unit; a read / write head ( 6 ) for reading and writing data on a data track ( 10 ) of a storage medium ( 5 ), which in use of the housing ( 2 ) of the unit is worn; one on the housing ( 2 ) of the unit attached actuator system ( 7 ) for causing a movement of the read / write head ( 6 ) in relation to the data track ( 10 ) to align the head to the data track, with the actuator system ( 7 ) has a plurality of degrees of freedom for effecting the movement; a control unit ( 12 ) for controlling the actuator system ( 7 ) to effect the movement; at least one on the housing ( 2 ) of the unit provided housing vibration sensor ( 8th ) to generate a signal indicative of vibrations of the housing; and at least one on the actuator system ( 7 ) provided actuator system vibration sensor ( 9 ) to generate a signal indicative of vibrations of the actuator system; the control unit ( 12 ), the signals from the housing and the actuator vibration sensor ( 8th . 9 ) to derive at least one coupling signal indicative of the vibratory coupling between the degrees of freedom, and about the actuator system ( 7 ) in dependence on the at least one coupling signal and the signal from the at least one housing vibration sensor ( 8th ) to control. A unit according to claim 1, wherein the control unit ( 12 ) is adapted to the coupling signal in dependence on the difference between the signal from an actuator vibration sensor ( 9 ) and the signal from a housing vibration sensor ( 8th ). A unit according to claim 1 or claim 2, wherein the control unit ( 12 ) a feed-forward logic ( 31 ) (For generating a control signal u _y) (for controlling the actuator system 7 ), the control logic ( 31 ), a first correction to the control signal in response to the signal from a housing vibration sensor ( 8th ) and apply a second correction to the control signal in response to a coupling signal (a _c ). Unit according to one of the preceding claims, wherein the read / write head ( 6 ) to the actuator system ( 7 ) is attached. Unit according to claim 4, comprising a first vibration sensor ( 9 ) arranged to absorb the vibrations of the actuator system ( 7 ), which is transmitted upside down ( 6 ). A unit according to claim 5, including a first housing vibration sensor ( 8th ) located on the housing ( 2 ) in the area of the head ( 6 ) to detect the vibrations of the housing being transferred to the head. A unit according to claim 6, wherein the unit is a tape drive and the actuator system is adapted to translate the head ( 6 ) in a transverse direction relative to the longitudinal data track (US Pat. 10 ) on the tape ( 5 ) and a rotary motion of the head ( 6 ) in relation to the data track ( 10 ) to counteract the skew between the head and the belt. A unit according to claim 7, wherein the actuator system ( 7 ), the head ( 6 ) to cause both the translational movement and the rotational movement. A unit according to claim 7 or claim 8, wherein the first actuator vibration sensor ( 9 ) and the first housing vibration sensor ( 8th ) are arranged to detect vibrations in the transverse direction. Unit according to claim 9, wherein the control unit ( 12 ) is adapted, a first coupling signal (a _c ) in dependence on the difference between the signals from the first actuator vibration sensor ( 9 ) and the first housing vibration sensor ( 8th ). A unit according to claim 10, wherein the control unit ( 12 ), the first coupling signal (a _c ) by subtracting the signal from the first housing vibration sensor ( 8th ) from the signal from the first actuator vibration sensor ( 9 ). A unit according to claim 10 or claim 11, wherein the control unit ( 12 ) a feed-forward logic ( 31 ) for generating a lateral position control signal (u _y ) for controlling the movement in the transverse direction by the actuator system ( 7 ), the control logic ( 31 ), a first correction to the lateral position control signal (u _y ) depending on the signal from the first housing vibration sensor ( 8th ) and apply a second correction to the lateral position control signal (u _y ) in response to the first coupling signal (a _c ). A unit according to any one of claims 5 to 12, wherein the first actuator vibration sensor ( 9 ) one Accelerometer for generating a signal indicative of acceleration. A unit according to any one of claims 6 to 13, wherein the first housing vibration sensor ( 8th ) has an accelerometer for generating a signal indicative of acceleration.

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